Lubricating oils



Patented May 31, 1938 PATENT OFFICE LUBRICATING OILS I Roger W. Richardson and John J. Owen, Baton Rouge, La., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing.

Application December 31, 1935,

Serial No. 57,013 7 Claims. (01. 87-2 The. present invention relates to lubricating oils and has for its principal object the provision of agents which may be added to'lubricati'ng oils to improve their characteristics and the provision of lubricating oils improved in this manner. More especially, the present invention is directed to the provision of a lubricating oil composition having a high resistance to oxidation and a low tendency to form separable sludge.

The susceptibility of a lubricating oil to oxidation at motor operating temperatures presents a serious problem to the refiner. Such oxidation re'sultsin theformation of oil soluble resinous products which cause piston ring sticking with its attendant evils. The susceptibility of an oil to oxidation at motor'operating temperatures is indicated by the amount of oxygen the oil will absorb in a given time at a temperature of 200 C.

The formation of separable sludge in a lubricating oil is also a result of oxidation. It appears to be due to the oxidation of different constituents from those which,-on oxidation, form resinous oil-soluble products. The former constituents form oxidation products which separate from the oil, thereby changing its viscosity and oiliness, and deposit in the crankcase of a motor, giving rise to troublesome gumming and resulting in poorlubrication.

The tendency of a lubricating oil to form separable sludge is indicated by a value known as the Sligh number of the oil which is determined by exposing a sample of oil of given volume to the action of a given quantity of oxygen at 392 F. The Sligh number of an oil is the number of milligrams of sludge deposited by 10 cos. of the oil when treated at the temperaturev specified for a given time with a given quantity of oxygen.

It has been attempted to increase the resistance of a lubricating oil to oxidation by adding to the oil an oxidation inhibitor such as aor b-naphthol, gossypol, aromatic S02 extracts of crude oils, or phenolic or other extracts thereof, complex organic compounds containing aromatic nuclei and/or containing sulfur, such as mercaptobenzothiazoles, and/or containing nitrogen,

such as dimethylaniline and certain leuco bases. In addition, certain organic petroleum mixtures produced by voltolization of naphthenic petroleums and of aromatic petroleum extracts have been found to be extremely efiicient oxidation inhibitors.

The majority of oxidation inhibitors, especially those which'are sufficiently inexpensive to be commercially feasible, such as those of natural origin, however, increase the tendency of an oilto which they are added to form separable sludge. Thus, in his effort to overcome one major evil, the refiner has been facedwith amagnification of another, and perhaps greater, evil.

It has now been found that the tendency of an oil to form separable sludge can be greatly minimized and in some instances completely eliminated by the addition to the oil of a small amount of an open chain alcohol of at least 10 carbon atoms, particularly aliphatic alcohols of at least 12 carbon atoms, and preferably aliphatic alcohols having from 15 to 25 carbon atoms. In addition, it has been found that alcohols of at least 10 carbon atoms, produced by voltolization of alcohols of lower molecular weight, preferably those of at least 8 carbon atoms, are'particularly useful for the stated purpose.

Mixtures of monomeric alcohols, such as those obtained by the liquid phase oxidation, of heavy hydrocarbon oils and waxes have not displayed satisfactory utility for the purpose of the present invention. A possible explanation for this fact may be the presence in such mixtures of other oxidation products such as lactones and aldehydes. For the purpose of the present invention, therefore, the alcoholic mixture employed may be said to be one which is unadulterated by other organic oxygen-containing compounds obtainable as by-products in the production of alcohols by the oxidation of hydrocarbons.

Some of the monomeric alcohols contemplated for use according to the present invention have been reported by previous investigators to exhibit anti-oxidant or oxidation inhibitor properties in transformer oils and have been sug-. gested by these investigators as additions to transformer oils to prevent the degradation thereof by oxidation. Transformer oils are, in general, of much lower viscosity than motor lubricating oils and function at low temperatures and are subjected to high electrical tensions.

It may be that in such oils these alcohols act as oxidation inhibitors. In lubricating oils for motor lubrication, however, these alcohols exercise no measurable effect on the rate of oxygen absorption of the oils. This fact conforms with the conclusion arrived at by repeated observation that the effectiveness as an oxidation inhibitor depends, to a large extent, upon the temperature at which it is employed, it having been demonstrated that a substance which acts as an oxidation inhibitor in oils which function at room temperature is entirely useless as oxidation inhibitors in oils which function at high temperatures. According to the present invention these alcohols are used in lubricating oils for motor lubrication not as anti-oxidants or oxidation inhibitors, but preferably in conjunction with an oxidation inhibitor.

, Other alcoholic bodies of open chain structure which are suitable for the purpose of the present invention are those containing at least 10 carbon atoms which have been prepared by chemical condensation of alcohols of lower molecular weight, preferably those having at least 6 carbon atoms. When the alcohols are of a saturated nature the condensation may be conducted by first chlorinating the alcohols in a known manner and then exposing them to the action of a condensing agent such as aluminium chloride. If the alcohols be initially unsaturated, the condensation in the presence of the metal halides can be carried out directly.

A more severe test for the sludge formation propensities of a lubricating oil than the Sligh test, known as the modified Sligh test, in which a greater amount of oxygen and a higher temperature than are used in the Sligh test are employed, has been adopted. Substances hitherto suggested for use as sludge formation inhibitors or sludge dispersers have exhibited no noticeable effect on the modified Sligh number of an oil. The alcoholic bodies proposed for use according to the present invention appreciably decrease the modified Sligh numbers of oils to which they are added.

More important, perhaps, is the fact that these alcoholic bodies counteract the tendency of oxi dation inhibitors, such as those of natural origin, to enhance the formation of separable sludge in lubricating oils. A highly desirable composition of matter according to the present invention, therefore, is a lubricating oil containing a small amount of an oxidation inhibitor, preferably an inexpensive one of natural origin and heterogeneous composition, and a small amount of an alcoholic body of the class defined above. For example, a highly desirable lubricating composition, according to the present invention, is a light, phenol-treated distillate of the lubricating range, 2% of a voltolized 5050 blend of mineral oil and fatty oil having a via/210 of about 1000 sec. Saybolt and having oxidation inhibiting properties, and 2% of cetyl alcohol. v

The voltolization of alcohols for the production of sludge formation inhibitors, according to the present invention, is effected, in general, in either a tube in which a glow discharge is set up and through which the alcohol is passed as a foam or in a drum having a rotating trommel which dips into a liquid body of the alcohol, picks up a thin film thereof and exposes it to a glow discharge.

In general, the temperature under which the voltolization is conducted is between and 250 F. A pressure ranging from 2 ccms. to 20 ccms. of mercury is maintained in the apparatus. The frequency of the alternating current employed may be between 500 and 15,000 cycles per second. The voltage impressed on the apparatus may be between 1500 and 10,000 volts. Usually the voltage employed is within the upper half of the range mentioned when the tube type voltolization apparatus is employed and in the lower half of the range specified when the rotating trommel type of apparatus is employed. The frequency of the alternating current usually varies inversely with the voltage.

In cases where the alcoholic body is not readily soluble in the lubricating oil, it may be rendered more soluble by being subjected to voltolization Oxidation inhibitors for lubricating oils were obtained according to the following methods:

No. 1.--A blend of 33% Coastal Red oil, 15% of b-naphthol and 50% of rapeseed oil was voltolized in a tube at a temperature of 180 F. under a pressure of 2 ccms. of mercury by the action of an alternating current of 10,000 cycles per second set up by a voltage of 5,000 volts until the blend had a viscosity of 840 sec. Saybolt/210 F.

No. 2.A blend of 50% of phenol plant extract and 50% of rapeseed oil was voltolized in a tube, under the conditions described above, to a viscosity of 1590 sec. Saybolt/210 F.

No. 3.-A blend of 49% of phenol plant extract, 49% of rapeseed oil and 2% of sulfur was voltolized in a tube, under the conditions specified above, to a viscosity of 1500 see. Saybolt/2l0 F.

No. 4.--A blend of 50% of lubricating oil of S. A. E. 50 grade and 50% of rapeseed oil was voltolized in a trommel type apparatus at a temperature of 180 F. under an absolute pressure of 4 ccms. of mercury by an alternating current of 10,000 cycles per second set up by 3000 volts to a final viscosity of 1037 sec. Saybolt/210 F.

Small percentages of any of the voltolization products described above decrease the oxidation rate of lubricating oils but tend to increase the Sligh number of said oils. In several tests these voltolization products were added in small amounts, not exceeding 10%, to a lubricating oil to determine their effect on the oxygen absorption rate and the Sligh number of said oil. Alcoholic bodies of the type described above were then added in small amounts to the several blends and to separate samples of the lubricating oil. The results of these tests are set forth in the following examples which are offered purely for purposes of illustration.

Example 1 A distillate lubricating oil, after receiving a light phenol treat, had a Sligh number of 1.4. 10 cos. of this oil absorbed, in successive 15 minute periods at 200 C., 126 ccms., 114 ccms. and 61 ccms. of oxygen respectively. 2% of stearyl alcohol, when added to this oil, reduced its Sligh number to 0.2 without having any appreciable effect on its oxygen absorption. A similar effect was produced by the addition of cetyl, lauryl and voltolized cetyl alcohols.

' The addition of 2% of oxidation inhibitor No. 1 to this oil increased its Sligh number .to 55.1 and reduced its oxidation rate to 2 ccms., 8 ccms. and 23 ccms., respectively. 1% of this oxidation inhibitor increased the Sligh number of theoil to 30. The addition of 2% of cetyl alcohol to this latter mixture reduced the Sligh number to 0.2.

Example 2 The distillate oil described in Example 1 containing 2% of oxidation inhibitor No. 2 described above had a Sligh' number of 34 and had an oxygen absorption rate in the first 15 minute period of 39 ccms.. The additionof 2% of cetyl her to 0.

Example 3 The lubricating oil described in Example 1 containing 2% of oxidation inhibitor No. 3 described above had a Sligh number of 37.3, a modified Sligh number of 195 and absorbed 15 ccms. of oxygen in the first 15 minute period. The addition of 2% cetyl alcohol to this mixture reduced the Sligh number to 0.6 and the modified Sligh number to 160.

Example 4 To a lubricating oil having a Sligh number of 12 2% of Voltolized cetyl alcohol having a viscosity of 600 sec. Saybolt at 210 F. was added. The Sligh number of the oil was reduced to 0.8. Voltolized stearyl alcohol and voltolized lauryl alcohol gave a comparable reduction in the Sligh' number. In the voltolization of these alcohols in a. tube the conditions employed were the same as those described above with the exception that a current of 1200 cycles per second was-set up by 8000 volts.

Example 5 The lubricating oil described in Example 1 containing 2% of oxidation inhibitor No. 4 described above had a Sligh number of 12.4 and absorbed 8'7 ccms. of oxygen in the first 15 minute period. The addition of 2% of stearyl alcohol to this mixture reduced the Sligh number to 0.2.

.The nature and objects of thepresent invention having been thus described and illustrated by specific embodiments thereof, which are obviously not intended to define the scope of this invention, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. A process for improving the oxidation characteristics of a lubricating oil which comprisesadding thereto an oxidation inhibitor and a small amount of an open chain alcohol having at least 10 carbon atoms and unadulterated by other oxygen-containing organic compounds formed as by-products in the production of alcohols by the oxidation of hydrocarbons.

2. A process according to claim 1 in which the oxidation inhibitor is one of natural origin which tends to increase the formation of separable sludge in the oil. r

3. A lubricating oil containing a small amount of an oxidation inhibitor and a small amount of an open chain alcohol having at least 10 carbon atoms and unadulterated by other oxygencontaining organic compounds formed as byproducts in the production of alcohols by the oxidation of hydrocarbons.

4. A lubricating composition having a high resistance to oxidation and a low Sligh number comprising a lubricating oil normally having a low resistance to oxidation and a high Sligh number, a small amount of an oxidation inhibitor having a tendency to increase the Sligh number of said lubricating oil and a small amount of an open chain alcohol having at least 10 carbon atoms and unadulterated by other oxygen-containing organic compounds formed as by-prodnets in the production of alcohols by the oxidation of hydrocarbons.

5. A composition according to claim 4 in which the alcohol is an aliphatic alcohol having between and 25 carbon atoms. I

6. A composition according to claim 4 in which the alcohol is a Voltolized aliphatic alcohol.

7. Acomposition according to claim 4 in which the alcohol is cetyl alcohol.

ROGER W. RICHARDSON. JOHN J. OWEN. 

